A slider is a good choice when you know that users think of the value as a relative quantity, not a numeric value. For example, users think about setting their audio volume to low or medium—not about setting the value to 2 or 5. — Microsoft
But that’s exactly what we’re trying to achieve - capture relative quantity, with users being able to place themselves in a spectrum in relation to others. And perhaps, after some discourse/debate, change their position “relative” to other spectrogram respondents.
I agree we can make the range smaller, I still think a “slider-like” UI is still better than buttons (see the screenshot above). The primary reason being is that one feature of the spectrogram is the ability to see how other users are on the spectrum. Can that be done with a button interface?